These children became ill at approximately 6:50 pm, while watching episode #38 of the original Pokemon cartoon. The Pikachu character successfully detonated incoming rockets, and the resulting explosions appeared as blue and red blasts of colour. It was also discovered in the later research that similar symptoms had occurred, although smaller in scale, during the airing of "YAT Anshin! Space Travel" story #25 on Saturday, March 29, 1997.

Formal experiments later confirmed that the rapid, rhythmic flashing of blues and reds triggered the seizures. The symptoms varied, and all affected children recovered soon after.

Paka paka was used in this particular scene. Illuminating the animation cell from behind during production photography creates a more radiant flash or light effect.
This is commonly used in the genre. In fact, paka paka was used in many previous episodes without (reported) incident. There were certainly other key factors at work, including the child's proximity to the television, light levels in the room, and the size of the screen.